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Control of industrial robots requires high speed data lines for transmitting commands to the various robot systems from the robot controller and for receiving status data of the various robot systems by the robot controller. Typically, current robot controllers utilize one or more high speed parallel data busses to communicate to and from the robot.
High speed parallel data buses require a single conductor for each data bit that is to be transferred to or from the various robot systems and the robot controller. For a high density and high speed transmission system there will be numerous conductors running between the robot controller and the various robot systems. Also, in addition to the data carrying conductors, a number of conductors will be required to carry overhead data such as read and write commands and system select commands. As the chassis and the physical size of various systems continues to decrease, space becomes a more valuable commodity. The use of a parallel data transmission system requires an increased pin count as more systems are linked together and/or larger data words are used. This increased pin count will result in larger interface interference between the pins and conductors that will need to be in close proximity to one another will increase as well. This increase in interference can result in increased complexity in terms of circuits and systems and increase the cost of these systems as well. In addition, as the physically available space decreases, the amount of space taken up by parallel conductor runs inside the chassis can reduce the internal air flow resulting in increased complexity and cost to ensure that proper cooling occurs. Also, purchasing, installing, maintaining, and trouble shooting multiple conductor parallel data communication can be a costly investment for any system. In addition, the time required to trouble shoot a malfunctioning parallel communication system increases with the number of conductors carrying data.
Therefore what is needed in the art is a simple data interface system that is easy to route within a chassis, robust in its ability to carry high speed data, and able to perform data error checking.
A fast serial interface including a three-wire network connection between a bus controller and one or more bus devices is disclosed. The bus controller processes and issues data packets across the three-wire network that include a command code, a bus device selection code, and a bus device register selection code. If the command code corresponds to write code, then the selected bus device stores the data contained within the packet in the selected register. If the command code corresponds to a read command, the selected bus device retrieves the data stored in the selected register, forms a read data packet and transfers the read data packet to the bus controller.
Additional aspects, features and advantages of the present invention are also described in the following Detailed Description.